Connecting rod and method for manufacturing the same

ABSTRACT

A connecting rod ( 1 ) has a small connecting rod eye ( 2 ) and a large connecting rod eye ( 3 ). A bearing shell ( 4, 5 ) is disposed in at least one connecting rod eye ( 2, 3 ), wherein the bearing shell ( 4, 5 ) is held in the connecting rod eye ( 2, 3 ) for secure mutual rotation therewith. To obtain good adhesion of the bearing shell ( 4, 5 ) in the connecting rod eye ( 2, 3 ), the bore surface ( 12, 13 ) in one connecting rod eye ( 2, 3 ) and/or the outer surface of a bearing shell ( 4, 5 ) has/have a structure ( 6, 7, 24, 26, 28, 30, 32, 34, 37, 38 ), wherein the structure ( 6, 7, 24, 26, 28, 30, 32, 34, 37, 38 ) is formed by elevations ( 9 ), the elevations ( 9 ) delimiting the outer periphery of depressions ( 8 ). In a method for producing a connecting rod ( 1 ) comprising at least one connecting rod eye ( 2, 3 ) with a structured surface ( 12, 13 ), wherein a bearing shell ( 4, 5 ) is disposed in the connecting rod eye ( 2, 3 ) after structuring of the surface, the surface ( 12, 13 ) is structured with a laser.

This application is related to EP 02 025 788.7 filed Nov. 16, 2002, theentire disclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The invention concerns a connecting rod and a method for producing aconnecting rod in accordance with the independent claims.

The book “Jahrbuch Schleifen, Honen, Läppen und Polieren” (annualgrinding, honing, lapping and polishing) by H.-W. Hoffmeister and H.-K.Tönshoff (publisher), Vulkan-Verlag Essen, 2002, pages 396 to 408discloses a holding groove on a connecting rod eye into which a nose,formed on the bearing shell, projects. The surface of the connecting rodeye is conventionally honed to improve the tight fit of the bearingshell.

It is the underlying purpose of the invention to produce a connectingrod of this type, which provides sufficient fixation of the bearingshell in the connecting rod eye even under high loads, and to propose amethod for producing a connecting rod having a long service life.

SUMMARY OF THE INVENTION

This object is achieved with a connecting rod having the features of theindependent claims.

Good fixation of a bearing shell in a connecting rod eye is ensured byproviding a surface structure in a connecting rod eye with depressionswhose outer periphery is delimited by elevations. The elevations on thestructured edges of the structure anchor the bearing shell in theconnecting rod eye. The structure may be a uniform pattern which can beadapted to the loads which occur and which can be reproduced duringmanufacture. The structure can be adapted to working loads in a simplemanner by changing the depth of the depressions and the height of theelevations.

The depressions with sideward elevations are suitably designed asfurrows. The furrows may advantageously be straight or cross each other.The furrows may also be wavy. The depressions may advantageously beformed as closed pockets. As viewed from above, the pockets mayadvantageously have an elongated or round shape. The inner surface of abearing shell and/or the surface of a component disposed in the bearingshell advantageously has/have a structure which is formed fromdepressions only. The depressions act as micro-pressure chambers whichfacilitate hydraulic lubrication to reduce friction between the slidingpartners.

The production of the connecting rod can be facilitated by structuringthe surface of a connecting rod eye using a laser. The laser structuringsimultaneously permits good adaptation of the structure to the workingloads. The elevations are formed by displaced melt produced duringprocessing at the structure edges, which is generated through thermalprocessing. The height of the elevations can be adjusted via thedisplaced melt volume. The melt volume can be varied by the processingparameters, i.e., for example, via the advance speed or via the laserparameters, i.e., for example, through adjustment of the power or thepulse duration. Laser processing facilitates changes to the design ofthe structure, such as the surface portion of pocket structures or theangles of intersection of crossing structures. The height and the widthof the elevations influence the adhesion of the bearing shell in theconnecting rod eye and can also be easily varied during laserprocessing.

Embodiments of the invention are explained below with reference to thedrawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a schematic perspective view of a connecting rod;

FIG. 2 shows a section through a large connecting rod eye with bearingshell disposed therein, and a crankshaft;

FIG. 3 shows the profile of a surface of a connecting rod eye along theline III-III in FIG. 4;

FIG. 4 shows a top view onto a section of a surface of a connecting rodeye;

FIG. 5 shows the profile of the surface of a connecting rod eye alongthe line V-V in FIG. 6;

FIG. 6 shows a section of a top view onto the surface of a connectingrod eye;

FIGS. 7 shows a schematic view from above of first surface structures;

FIGS. 8 shows a schematic view from above of second surface structures;

FIGS. 9 shows a schematic view from above of third surface structures;

FIGS. 10 shows a schematic view from above of fourth surface structures;

FIGS. 11 shows a schematic view from above of fifth surface structures;and

FIGS. 12 shows a schematic view from above of sixth surface structures.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The connecting rod 1, schematically shown in FIG. 1, has a smallconnecting rod eye 2 and a large connecting rod eye 3. For use in acombustion engine, a piston pin is conventionally disposed in the smallconnecting rod eye 2 and the crankshaft is disposed in the largeconnecting rod eye 3. A bearing shell 4 is disposed in the smallconnecting rod eye 2, and a bearing shell 5 is disposed in the largeconnecting rod eye 3. To rigidly fix the bearing shells 4, 5 in theconnecting rod eyes 2, 3, the bore surfaces 12 and 13 of the connectingrod eyes 2 and 3 have structures 6 and 7. The structures 6 and 7increase the adhesion of the bearing shells 4 and 5. Instead of or inaddition to the structures 6, 7 of the bore surfaces 12, 13, the outersurfaces of the bearing shells 4, 5 which are in contact with the boresurfaces 12, 13 may have corresponding structures. The friction betweenthe inner side of the bearing shells 4 and 5 and the piston pin or thecrankshaft should be minimized. To reduce friction, the inner surface 21of the bearing shell 4 has a structure 22 and the inner surface 18 ofthe bearing shell 5 has a structure 20.

To fix a bearing shell 4, 5 in a connecting rod eye 2, 3, a nose 15 maybe disposed on the outer periphery of a bearing shell, in addition tothe structure 6, 7, as exemplarily shown in the bearing shell 5 of FIG.2. The nose 15 extends radially outwardly at the outer periphery of thebearing shell 5. In the region of the nose 15, the connecting rod eye 3of the connecting rod 1 has a holding groove 14 into which the nose 15projects. The surface 13 of the connecting rod eye 3 additionally has astructure (not shown in FIG. 2). The crankshaft 16 is disposed in thebearing shell 5 and rotates in the direction of the arrow 17. While thefriction between bearing shell 5 and connecting rod eye 3 should be aslarge as possible to rigidly hold the bearing shell 5 in the connectingrod eye 3, the friction between the bearing shell 5 and the crankshaft16 should be as small as possible. Towards this end, the inner surface18 of the bearing shell 5 has a structure 20 (shown in FIG. 1). Astructure corresponding to the structure 20 may be provided on the outersurface 19 of the crankshaft 16 rather than on the inner surface 18.

FIGS. 3 and 4 show, in an enlarged scale, a structure 37 of a surface 39which may be the surface 12, 13 of a connecting rod eye 2, 3. Thestructure 37 may be provided in the small connecting rod eye 2 and/or inthe large connecting rod eye 3. The structure 37 is introduced into thesurface 39 which has a basic structure 23. The structure 37 isadvantageously produced with a laser. The basic structure 23 may e.g. bea cross structure produced through honing. The basic structure 23 mayalso consist of peripheral furrows produced during spindling of thesurface 39. Elongated pockets 11 are introduced into the basic structure23 at regular intervals which are formed by a depression 8 whoseperiphery is delimited by a circumferential elevation 9. The depressions8 have a depth a relative to the surface 39 while the elevations 9extend beyond the surface 39 by a height b. The elevations 9 have awidth c and the depressions 8 have a width d. The depth a and the heightb advantageously are approximately up to 50 μm. The width c, d isadvantageously selected to be ≦50 μm.

FIGS. 5 and 6 show an embodiment of a structure 38 of the largeconnecting rod eye 3 which may be introduced into the surface 12, 13 ofthe connecting rod eye 2, 3 and is formed by round pockets 10. The roundpockets 10 are suitably uniformly introduced into the surface 40. Theround pockets 10 have a circular depression 8 whose outer periphery isalso surrounded by a circular elevation 9. The round pockets 10 are alsointroduced into a surface 40 having a basic structure 23.

FIGS. 7 through 12 show examples of an arrangement of a structure on asurface. The double arrow 36 thereby designates the peripheral directionof the connecting rod eye or of the bearing shell. In the structure 24shown in FIG. 7, the pockets 25 are disposed in a regular pattern. Thepockets 25 may have a depression 8 and an elevation 9, in correspondencewith the round pockets 10 shown in FIGS. 5 and 6. The structure 24 issuitably introduced on the bore surface 12 of the small connecting rodeye 2 or the bore surface 13 of the large connecting rod eye 3. It mayalso be appropriate to provide pockets 25 without elevations 9. Suchpockets reduce the friction between the sliding partners, since they areused as a lubricant reservoir thereby permitting full hydrodynamiclubrication. The pockets simultaneously act as micro-pressure chambers.Pockets 25 of such a design are suitably disposed on the inner surface21 of the bearing shell 4 and/or on the outer periphery of a piston pinand on the inner surface 18 of the bearing shell 5 and/or the outersurface 19 of the crankshaft 16.

FIG. 8 shows elongated pockets 27 which extend approximately in aperipheral direction. The elongated pockets 27 are disposed at regularintervals and form a structure 26. The structure 28 of FIG. 9 is formedby elongated pockets 29 which extend approximately transversely to theperipheral direction. It may also be suitable to provide elongatedpockets which subtend an angle of between 0° and 90° with respect to theperipheral direction. The structures 26 and 28 may be disposed on theinner surface 18 of the bearing shell 5 or the outer surface 19 of thecrankshaft 16 and/or the inner surface 21 of the bearing shell 4 or theouter surface of a piston pin. The pockets 27 and 29 are therebysuitably formed only as depressions. The pockets 27 and 29 may each bedelimited at their outer periphery by an elevation 9. Pockets 27 and 29of this design increase friction and are preferably disposed on thesurface 12 of the connecting rod eye 2 or the surface 13 of theconnecting rod eye 3.

The structure 30 of FIG. 10 is formed by crossing furrows 31 which areeach delimited by elevations 9. The furrows 31 have an angle ofintersection a. The structure 30 is suitably formed on a surface 12, 13of a connecting rod eye 2, 3. The adhesion of the structure 30 may beinfluenced by varying the angle of intersection α. FIG. 11 shows astructure 32 having wavy furrows 33. The outer periphery of the furrows33 also comprises elevations 9. The furrows 33 are suitably disposed onthe surfaces 12 and 13 of the connecting rod eyes 2 and 3. FIG. 12 showsa structure 34 with furrows 35 which extend parallel to each other. Thefurrows 35 are disposed approximately perpendicularly to the peripheraldirection in FIG. 12. The furrows 35 may suitably subtend an angle ofless than 90° with respect to the peripheral direction. The furrows 35may also have elevations 9 at their outer periphery to increase thefriction between connecting rod eye 2, 3 and bearing shell 4, 5.

A connecting rod 1 is advantageously produced by structuring the surface12, 13 of one or both connecting rod eyes 2, 3 using a laser. Thesurface 12, 13 is advantageously fine machined before laser structuringthereby producing a basic structure 23 into which the structure isintroduced. For pocket structures 10, 11, 24, 26, 28, the adhesion of astructure 6, 7 on the surface 12, 13 of a connecting rod eye 2, 3 may begreatly influenced by the surface portion. For cross structures 30, theadhesion can be changed by varying the angle of intersection α. Theheight b of the elevations 9 and the width of the elevations 9 have aninfluence on the adhesion of all structures.

1. A connecting rod comprising: a first end having a small connectingrod eye; a second end cooperating with and spaced apart from said firstend, said second end having a large connecting rod eye; and at least onebearing shell disposed in said small and/or said large connecting rodeye for secure mutual rotation therewith, wherein at least one of aninner surface of said small and/or said large connecting rod eye and anouter surface of said at least one bearing shell has a structure, saidstructure having elevations adjacent to and delimiting depressions. 2.The connecting rod of claim 1, wherein said depressions are formed asfurrows.
 3. The connecting rod of claim 2, wherein said furrows aredisposed in straight lines.
 4. The connecting rod of claim 2, whereinsaid furrows are disposed to cross.
 5. The connecting rod of claim 2,wherein said furrows are wavy.
 6. The connecting rod of claim 1, whereinsaid depressions are formed as closed pockets.
 7. The connecting rod ofclaim 6, wherein, as viewed from above, said pockets have an elongatedor round shape.
 8. The connecting rod of claim 1, wherein an innersurface of said bearing shell and/or an outer surface of a componentdisposed in said bearing shell has a structure which is only formed fromdepressions.
 9. A method for producing a connecting rod, the connectingrod having a first end defining a small connecting rod eye, a second endcooperating with and spaced apart from said first end, said second enddefining a large connecting rod eye, and at least one bearing shelldisposed in said small and/or said large connecting rod eye for securemutual rotation therewith, the method comprising the step of:structuring at least one of an inner surface of said small and/or saidlarge connecting rod eye and an outer surface of said at least onebearing shell, said structuring having elevations adjacent to anddelimiting depressions.
 10. The method of claim 9, wherein said innersurface is structured by a laser.